1. Field of the Invention
The invention relates to a liquid crystal display (LCD) device, more particularly to a liquid crystal display (LCD) device using the COA process.
2. Description of the Related Art
The conventional TFT-LCD panel was assembled by a TFT glass substrate, a color filter glass substrate, and the liquid crystal injected into the gap between such two substrates. In the past, the alignment between the TFT glass substrate and the color filter glass substrate must be made accurately. Therefore, the yield of the cell process is the lowest one in comparison to the whole panel process. If we can prevent from the loss under such process, the whole yield and the cost reduction can be improved greatly. For the new mass production technology, which is the so-called COA (color filter on array) technology, the color filter process should be executed after the TFT array process for the TFT glass substrate. By means of the COA technology, higher aperture ratio of the TFT glass substrate is obtained, thus improving the brightness of the panel effectively.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is the cross-sectional view for the conventional TFT-LCD device. The TFT glass substrate 11 and the color filter glass substrate 12 are adhered each other. There are a plurality of TFTs 111 on the TFT glass substrate 11. Each TFT 111 is corresponding to one pixel electrode 112. The transparent dielectric layer 113 is put between the TFTs 111 and the pixel electrodes 112. There are a plurality of color filters 121 in the red (R), green (G), and blue (B) color on the color filter glass substrate 12. The black matrix (BM) 122 separates every two color filters in order to prevent from light leakage. A transparent common electrode 123 is disposed on the color filters 121. A liquid crystal layer 13 is injected into the gap between the TFT glass substrate 11 and the color filter glass substrate 12.
FIG. 2 is the cross-sectional view for the TFT-LCD device using the COA technology. The bottom glass substrate 21 and the top glass substrate 22 are adhered each other. There are a plurality of TFTs 211 on the bottom glass substrate 21. Each TFT 211 is corresponding to one pixel electrode 212. There are a plurality of color filters 213 in the red (R), green (G), and blue (B) color between the TFTs 211 and the pixel electrodes 212. The black matrix (BM) 214 separates every two color filters in order to prevent from light leakage. A transparent common electrode 221 is disposed on the top glass substrate 22. A liquid crystal layer 23 is injected into the gap between the bottom glass substrate 21 and the top glass substrate 22.
FIG. 3 illustrates the structure of the TFT device using the COA technology. The black matrix (BM) area 32 is around the active area 31, the wire-collecting area 33 is adjacent to the BM area 32, and the outer lead bonding (OLB) area 34 is adjacent to the wire-collecting area 33. The active area 31, the wire-collecting area 33 and the OLB area 34 are connected electrically. Metal wires in the active area 31 are protected by a passivation layer. However, there is no passivation layer to protect metal wires in the wire-collecting area 33 and the OLB area 34. Therefore, metal wires in the wire-collecting area 33 and the OLB area 34 are exposed and easily invaded by moisture. It may result in poor product reliability.